Scientists working on the next generation of OLED technology have discovered that making these devices more efficient is not as simple as squeezing as much light as possible out of them.
A new study reveals that there is a delicate balance between trapping light inside an OLED and letting it escape, and pushing the system too far can actually reduce performance.
OLEDs, or organic light-emitting diodes, are already used in many modern TVs, smartphones, and wearable devices.
They are thinner, lighter, and more flexible than traditional LEDs, and they can be made using materials that are easier to recycle.
However, some types of OLEDs that avoid using rare heavy metals are still quite inefficient, with as much as three-quarters of the electrical energy turning into heat instead of light.
To improve efficiency, engineers often place OLEDs inside tiny structures called optical microcavities.
These cavities trap light in a small space, forcing it to bounce around until it escapes as useful brightness rather than being lost as heat.
One researcher compared the process to squeezing toothpaste from a tube: the tighter the squeeze, the faster the light comes out.
But the new research shows that this strategy has limits. When light is squeezed too tightly, it begins to strongly interact with the molecules that produce the light.
This interaction creates unusual mixed states known as polaritons, which combine properties of both light and matter.
Scientists have known about these states for some time, but they did not fully understand how they affect the way energy moves inside OLEDs.
The research team developed a new theoretical model explaining what happens as the squeezing increases.
Their results show that once polaritons form, efficiency can start to drop. Although polaritons can emit light very quickly, they spread the energy across a huge number of molecules.
This dilution weakens the processes that feed energy into the light-emitting states. Efficiency can fall even further if the energy of the polaritons drifts too far from the natural energy levels of the molecules.
In simple terms, the study suggests that the best performance comes from finding the “sweet spot” where the cavity enhances light output without over-compressing the system.
The researchers also propose new device designs that reduce the number of molecules sharing these states from hundreds of thousands to only a few. Such designs could potentially lead to record-breaking efficiency in future OLED displays and lighting.
The work, carried out at the University of Turku in Finland and published in the journal Materials Horizons, provides a clearer roadmap for engineers trying to build more sustainable and energy-efficient screens.
As OLED technology continues to evolve, understanding this balance could help create brighter devices that use less power and last longer, benefiting everything from smartphones to large televisions.
